Coal-cutting chisel with hard metal cutting edge



Patented May 9, 1933 UNITED STATES PATENT-OFFICE ADOLF MEUTSCH, OFESSEN, GERMANY, ASSIGNOR T0 GEWERKSCHAIT WALLRAM,

' OF ESSEN, GERMANY COAL-CUTTING CHISEL WITH HARD METAL CUTTING EDGEApplication filed august 20, 1930; Serial No. 476,473, and in GernianyMay 6, 1930.

The present invention relates to picks for coal-cutting machinesprovided with inserted hard metal cutting-edges to keep sharp longer,and particularly to picks employed in coaLcutting machines of the barand chain type. In view of the extraordinary stresses to which picks forcoal-cutting machines are subjected by impact and breaking effects dueto inequalities in the structure of the material to be cut, andespecially to pipes or funnels of iron pyrites embedded therein, it wasting chisel with inserted hard metal cuttingranged in a bore of thepick.

edge by inserting the latter in the chisel member so that itis supportedrelative to both the cutting pressure and the tilting moments producedthereby. The efliciency of the new coal-cutting pick is increasedfurther by providing-means for keeping the pick always in proper cuttingposition.

Several embodiments of the new invention are illustrated in theaccompanying drawing, in which: 7

Figure 1 is a side-view of a pick for a coalcutting machine of the bartype, in which the hard metal piece is received by a milled groove.

Figure 2 is a front-view thereof.

Figure 3 is a top-view thereof.

Figures 4a and 4b disclose a section on the line IV-IV, of Fig. 1, seenfrom above, with two different forms of cross-section of the hard metalpiece. I

Figure 5 is .a side-view, partly in section, of a pick for acoal-cutting machine of the bar type, in which the hard metal piece isar- Figure 6 is a front-view thereof. Figure 7 is a side-view of a plckfor a coal cutting machine of the chain type and Figure 8 is a top-viewthereof.

In the modification shown in Fig. 1 the coal-cutting chisel is flattenedon both sides of its front end 1 and provided with a continuous milledgroove 2 inclined towards the longitudinal direction of the pick andadapted to receive the hard metal piece 3 so that the front upper' endthereof remains free to serve as cutting-edge, the free front surface-4of the hard metal piece being kept consideraby smaller than the uppersurface 5 in order to provide a suifciently broad cut ting surface 5 inconnection with a suflicient support by the front portion of the chisel."lhecomponents of cutting pressure are fully supported and, furthermore,the t lting moments acting approximately in the direction of the arrowandendangering the connection of the hard metal piece with the chiselare safely taken up by the overla ping chisel portion. The cross-sectionof t e slot "2 may be rectangular (Fig. 4a) ,thoughit is preferred togive it the form shown in Fig.

4b where it is broader in the centre than on the sides so as to protectthe hard metal piece against any lateral stresses also. Par-' ticularlypreferred is the rounded or circularform of cross-section, which avoidssharp corners favouring the formation of cracks owing to continuousstrain and permits convenient production of the slot as a bore.

Owing to the considerably increased stressing of the coal-cutting pickdue to the use of hard metal as cutting-edge, special and ampleprovisionmust be made for preventing the coal-cutting pick inserted inthe band by means of an ordinary conical bolt 7 from moving. In themodification according to Fig. 1 the cross-cutting pick is thus providedwith an eccentric projection 8 which fits into a corresponding clearance9 in the bar 6. As the eccentricity of the projection is directeddownwardly, the moment'of resistance of the pick relative to the'bendingstresses of-the cutting pressureis simultaneously increased v toa considerable extent.

Furthermore, provision is made also for preventing as much as possiblethe development of torsional stresses during cutting by disposing theedge 5 of the hard metal piece on a plane extending within or below theaxis 10 of the bolt 7. To return the coal-cutting pick if moved out ofits correct turning position by extraordinary strain,'the flattened ofanother drawback of the known kinds of of tools, which hasto do withfrequent damaging of the hard metal piece or of the front portions ofthe chisel when the. coal-cutting pick is knocked into the bar 6. Sincethe cutting portions are lowered, it is possible to protide the pickwith a broad striking surface 11' which excludes any possibility ofdamaging the cutting parts when driving in the chisel. In themodification shown in Figs. 5 and 6 the simplified production of thecoal cutting .pick is emphasized, the front chisel portion 13, which hasthe form of'a bilaterally fiattened truncated cone projecting from thecollar '12, being provided with a. prismatic or cylindrical bore 14wherein the prismatic or cylindrical hard metal piece 3 is soldered.'The hard metal piece is thus inserted 1n the pick in such a way that,with the exception of one end surface, it is surrounded on all sldes bythe chisel to which it can be soldered everywhere so that the connectioncannot be severed even by any transverse stresses. The conical shape ofthe chisel portion 13 permits convenient removal of the chisel metalduring I regrindingof the edge 15, as the chisel cone :can be handledlike the wood of a lead pencil.

As the slope of the chisel cone corresponds approximately to theinclination of the hard metal piece 3, the height of the supportingchisel portion being in front never vanes 1n spite of regrinding. Thismodification may bolt.

be provided also with an eccentric projection 8 (Fig. 1), and in acorresponding construc tion of the front chisel portion the cuttingedgemay be disposed, as in Fig. 1, on a plane extending along or below theaxis 10 of the The collar 12 serves further for facilitating theattachment and removal of the pick. The front face 16 of the collar 12is kept broad enough to permit a pipe to be put thereon during drivingin. The transition from the surface 16 to the chisel portion is hollowedout considerably to prevent the formation of cracks which would surelydevelop, owing to high continuous strains, if the transition weresharp-cornered. I

The modification according to Figs. 7 and 8 relating to coal-cuttingpick of prismatic cross-section for a coal-cutting machine of t e chain,type discloses 'an attachment of t eha'rd metal bouy 3"sifnilar to themodification according to Fig. 1, and the form of cross-section inparticular maybe chosenac- I cording to Fig. 4b.

Picksas described cannot be utilized up to the limit of efiiciency oftheir hard metal cutting edges, since the great stresses which theinsertions will withstand, owing to the peculiar described arrangement,exceed the strength of the chisel itself. Particularly the chisel metaltaking up the components of cutting pressure is exposed to such' greatunit pressure as to be forced away when cutting pressure is at itshighest. Furthermore, in the portion of the pick projecting from the baror chain in the coal-cutting ma chine excessive bending strains areproduced by the blows during the cutting operation, and the grindingeffect due to 'the cross-feed of the pick acts destructively on thelateral surfaces of the latter so that the bearing strength of the pickhead is reduced quickly. 'As to the form of invention shown in Fig. 1,under increased strain the pick portion 17 positioned under thehardmetal portion will be forced away, thepickbreak off within the zoneindicated by the line18,:or the. side surfaces ground off rapidly.

These drawbacks are eliminated by hardening the surface layer of thepick metal sup 1 6' porting the hard metal insertion and of the pickportion chiefly exposed to bending and grinding so that the' surfacepressure available for supporting the hard metal insertion issufliciently large and, on the other hand, sufficient toughness of thepick relative to impacts and ample resistance to insured.

It was hitherto impossible to provide a hardened body portion for picks,since .oxidation processes and quenching, in view of the high hardeningtemperatures, had a crushing or generally" damaging effect upon the hardmetal portion. However, the damaging effects of high hardeningtemperatures are eliminated by the described universal embedding of thehard metal insertion and by the hardening and productionprocessesdescribed below, and a useful hardened coal cutting pick withhard metal insertion is produced possessingsuperior efficiency comparedwith unhardened ones.

In order to make it possible to harden the pick provided with a hardmetal insertion, the swaged blank, as indicated by the hatched grindingare lines Figs. 1, 3 and 4, is overdimensioned in its front portion soas to universally enclose-v the hard metal piece after the clearance 2has been milled or drilled while its upper end is disposed somewhatbelow the opening 19 of the clearance 2. The hard metal piece may beprovided with its final working surfaces already at the time when it isintro-- duced from above, and when the copper solder is poured in, thehollow space 20 formed in this manner is filled with copper solder tosuch an extent that the hard metal piece is on within a surface layermeasuring some millimetres, the superfluous portions in front of thechisel and of the solder are removed until the chisel has the formindicated by the full lines, and the cutting edge and perhaps the sidesurfaces of the hard metal piece are exposed.

What is claimed is 1. In a coal cutting pick with hard metalcutting edgea recessed front pick portion, a staff-like hard metal piece inserted insaid front pick portion and fastened to it by soldering, and metal partsof said front pick portion completely overhangin the foremost boundarysurface of the har metal piece adapted to support the tilting forcesproduced by the cutting pressure.

for protecting the said hard metal 2. Ina coal-cutting pick with hardmetal .cutting edge, a recessed front pick portion, and a staff-likehard metal piece inserted in the said front pick portion and fastened toit by soldering, the recess being inclined towards the longitudinaldirection of the pick and adapted to receive the said hard metal pieceso as to leave a cutting edge free on the front upper end thereof.

3. In a coal-cutting pick'with hard metal cutting edge, a recessed frontpick portion, and a staff-like hard metal piece inserted in the saidfront pick portion and fastened to .it by soldering, the recess beinginclined towards the longitudinal direction of the pick and adapted toreceive the said hard metal iece so as to leave a cutting edge'free onthe iiiont upper end thereof and being wider in cross-section in thecenter than on the sides piece against lateral stresses.

4. In a.- c'oal-cuttin pick with hard metal cutting edge, a pick ontportion, a boring in the said front portion Inclined towards the lon'tudinal direction of the ick, and a cylindrical staff-like hard metapiece inserted in the boring and fastened to the pick by soldering, thesaid hard metal piece being covered on all sides by the pick metal withthe exception of the upper front end surface.

h, 5. In a coal-cutting pick, a hard metal piece, and a front pickportion having a re-.

cess;for receiving the said hard metal piece, the recess being inclinedtowards the axis of the body of the pick and the supporting portion ofthe pick extending correspondingly parallel therewith and maintainingapproxi mately the same height during regrinding of tion havin the she eof a truncated cone, and a hat metal p1ece inserted in the said pick,the truncated cone shape of the, said pick facilitatin removal of thepick metal during regrin 'ng while maintaining the universal support ofthe hard metal p1ece.

. 7. In a coal-cutting machine, a pick, a bar for inserting the icktherein, a bolt for hold ing the pick, an a cutting ed e on the saidpick disposed on a lane extending below the axis of the said be t toprevent the development of torsional moments.

8. In a coal-cutting machine, a ick, a bolt thereon, and the flattenedsides 0 the front portion of the said pick located below the axis of thebolt being almost parallel and downwardly extended to push back, incooperation with the cutting groove in the coal, the ick into correctturning position if displace I by extraordinary strains. I

9. In a coal-cutting machine, a pick and a collarattached to the pick,the collar having an annular front driving face extending through aflute into the front pick portion.

10. A. coal-cutting pick comprising a hard metal insertion connected tothe ick metal by soldering and su'rface-hardene pick portlons, the saidpick portions supporting the hard metal insertion and being exposed tobending and grinding stresses to insure ample unit pressure for suporting the said hard metal insertion, sufiiclent toughness of the pickrelative to impact stresses, and ample resistance to grinding stresses.

11. In a coal cutting machine a pick, a bar for inserting the picktherein, a bolt for holding the pick, a projection on the bolt in theform of a cylindrical disc having a greater diameter than the bolt and'the axis of which is disposed below the axis of the bolt,

"and a cylindrical recess in the bar fitting over the said projection.

The foregoing s ification signed at C0-' logne, Germany this lst day ofAugust 1930.

ADOLF MEUTSCH.

' let 6. In a coal-cutting pic a front pick por-

